2.Data对象

获取时 分 秒 的封装

  var date=new Date();
 var h=date.getHours();
 var f=date.getMinutes();
 var m=date.getSeconds();
 var sum=hNum(h)+":"+hNum(f)+":"+hNum(m);
 console.log(sum);
function hNum(num){
    if(num<10){
        num="0"+num;
    }
    return num;
}

倒计时

    <div id="app"></div>
    <script>
        setInterval(go,1000);
  function go(){
 var app =document.querySelector("#app")
    var date=new Date();
 var h=date.getHours();
 var f=date.getMinutes();
 var m=date.getSeconds();
 var sum=hNum(h)+":"+hNum(f)+":"+hNum(m);
 app.innerHTML=sum
 console.log(sum);
}
function hNum(num){
    if(num<10){
        num="0"+num;
    }
    return num;
}

解析字符串获取距离时间戳

 var s="2021:10:13,18:00:00";
//    var arr=s.replace(","," ");
//     console.log(arr.slice(","));    
  s=s.split(",");
var arr=[];
var reg=/\:/g;
 arr[0]= s[0].replace(reg,"-");
 arr[1]=s[1];
 var list=arr.toString()
 list=list.replace(","," ");
 var startTime=(new Date()).getTime();
 var endTime=(new Date(list)).getTime();
 var gapTime=endTime-startTime;
//获取多少秒
var seconds=gapTime/1000;
 //获取小时
  var h=Math.floor(seconds/60/60);
 //获取相差秒数
  var mm=seconds-h*3600;
  //获取分钟数
  var f=Math.floor(mm/60);
  //获取秒数
  var m=Math.floor(mm-f*60);
 console.log(m);
  console.log(h);
console.log(f);
console.log("距离上晚自习还剩下"+h+"小时"+f+"分钟"+m+"秒");